A lighting device for a vehicle is used in different applications including head lamps, fog lamps, tale lamps, break lamps, and turn signal lamps. The vehicle includes passenger vehicles, motorcycles, bicycles, construction vehicles, and aircrafts. The lighting device has a light source, such as an incandescent lamp and a halogen lamp, a reflector, and a lens to obtain desired characteristics of the light distribution.
The incandescent lamp and the halogen lamp are not efficient in converting electricity to light. Thus, a large amount of electricity is required to produce light of desirable intensity. This may lower the fuel economy in an engine-driven vehicle and the mileage per charge in an electric vehicle.
Furthermore, lifetimes of the incandescent lamp and the halogen lamp are normally shorter than a lifetime of a vehicle. Thus, the number of periodical replacement of the lamps increases according to the period that the vehicle is used, that is, the number of times that the lamp is used. Even when a high intensity discharge (HID) lamp that has a longer lifetime than the halogen lamp is used, periodical replacement of the lamp is required. If daytime-lighting becomes mandatory for safety, the lifetime of the lamps may become a critical issue.
To solve the above-described problems, lighting devices using light emitting diodes (LEDS) as light sources are suggested in JP-A-10-228803, JP-A-2001-291901, JP-U-3080310, JP-A-10-109587, JP-A-2001-126510, JP-U-6-53294, JP-A-2000-331508, JP-A-7-288011, and JP-A-2000-58925. The LEDs is highly efficient in converting electricity to light and has long lifetimes. On the other hand, the LEDs have narrow lighting areas and small angles. Thus, lighting devices constructed of LEDs, a reflector, and a lens cannot provide desirable light distribution.
In JP-A-2001-291901, it is suggested that a plurality of LEDs are mounted in a lens and the lens is shaped so that desirable light distribution is produced. In JP-A-10-228803, it is suggested that focal distances of convex lenses of LEDs are adjusted to the same length to produce desirable light distribution. However, the suggested lighting devices do not provide much flexibility in altering light distribution.